text: /*
   * QEMU Block driver for  NBD
   *
   * Copyright (C) 2008 Bull S.A.S.
   *     Author: Laurent Vivier <Laurent.Vivier@bull.net>
   *
   * Some parts:
   *    Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  #include "nbd-client.h"
  #include "qemu/sockets.h"
  
  #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs))
  #define INDEX_TO_HANDLE(bs, index)  ((index)  ^ ((uint64_t)(intptr_t)bs))
  
  static void nbd_recv_coroutines_enter_all(NbdClientSession *s)
  {
      int i;
  
      for (i = 0; i < MAX_NBD_REQUESTS; i++) {
          if (s->recv_coroutine[i]) {
              qemu_coroutine_enter(s->recv_coroutine[i], NULL);
          }
      }
  }
  
  static void nbd_teardown_connection(BlockDriverState *bs)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
  
      /* finish any pending coroutines */
      shutdown(client->sock, 2);
      nbd_recv_coroutines_enter_all(client);
  
      nbd_client_detach_aio_context(bs);
      closesocket(client->sock);
      client->sock = -1;
  }
  
  static void nbd_reply_ready(void *opaque)
  {
      BlockDriverState *bs = opaque;
      NbdClientSession *s = nbd_get_client_session(bs);
      uint64_t i;
      int ret;
  
      if (s->reply.handle == 0) {
          /* No reply already in flight.  Fetch a header.  It is possible
           * that another thread has done the same thing in parallel, so
           * the socket is not readable anymore.
           */
          ret = nbd_receive_reply(s->sock, &s->reply);
          if (ret == -EAGAIN) {
              return;
          }
          if (ret < 0) {
              s->reply.handle = 0;
              goto fail;
          }
      }
  
      /* There's no need for a mutex on the receive side, because the
       * handler acts as a synchronization point and ensures that only
       * one coroutine is called until the reply finishes.  */
      i = HANDLE_TO_INDEX(s, s->reply.handle);
      if (i >= MAX_NBD_REQUESTS) {
          goto fail;
      }
  
      if (s->recv_coroutine[i]) {
          qemu_coroutine_enter(s->recv_coroutine[i], NULL);
          return;
      }
  
  fail:
      nbd_teardown_connection(bs);
  }
  
  static void nbd_restart_write(void *opaque)
  {
      BlockDriverState *bs = opaque;
  
      qemu_coroutine_enter(nbd_get_client_session(bs)->send_coroutine, NULL);
  }
  
  static int nbd_co_send_request(BlockDriverState *bs,
                                 struct nbd_request *request,
                                 QEMUIOVector *qiov, int offset)
  {
      NbdClientSession *s = nbd_get_client_session(bs);
      AioContext *aio_context;
      int rc, ret, i;
  
      qemu_co_mutex_lock(&s->send_mutex);
  
      for (i = 0; i < MAX_NBD_REQUESTS; i++) {
          if (s->recv_coroutine[i] == NULL) {
              s->recv_coroutine[i] = qemu_coroutine_self();
              break;
          }
      }
  
      assert(i < MAX_NBD_REQUESTS);
      request->handle = INDEX_TO_HANDLE(s, i);
      s->send_coroutine = qemu_coroutine_self();
      aio_context = bdrv_get_aio_context(bs);
  
      aio_set_fd_handler(aio_context, s->sock, false,
                         nbd_reply_ready, nbd_restart_write, bs);
      if (qiov) {
          if (!s->is_unix) {
              socket_set_cork(s->sock, 1);
          }
          rc = nbd_send_request(s->sock, request);
          if (rc >= 0) {
              ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov,
                                  offset, request->len);
              if (ret != request->len) {
                  rc = -EIO;
              }
          }
          if (!s->is_unix) {
              socket_set_cork(s->sock, 0);
          }
      } else {
          rc = nbd_send_request(s->sock, request);
      }
      aio_set_fd_handler(aio_context, s->sock, false,
                         nbd_reply_ready, NULL, bs);
      s->send_coroutine = NULL;
      qemu_co_mutex_unlock(&s->send_mutex);
      return rc;
  }
  
  static void nbd_co_receive_reply(NbdClientSession *s,
      struct nbd_request *request, struct nbd_reply *reply,
      QEMUIOVector *qiov, int offset)
  {
      int ret;
  
      /* Wait until we're woken up by the read handler.  TODO: perhaps
       * peek at the next reply and avoid yielding if it's ours?  */
      qemu_coroutine_yield();
      *reply = s->reply;
      if (reply->handle != request->handle) {
          reply->error = EIO;
      } else {
          if (qiov && reply->error == 0) {
              ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov,
                                  offset, request->len);
              if (ret != request->len) {
                  reply->error = EIO;
              }
          }
  
          /* Tell the read handler to read another header.  */
          s->reply.handle = 0;
      }
  }
  
  static void nbd_coroutine_start(NbdClientSession *s,
     struct nbd_request *request)
  {
      /* Poor man semaphore.  The free_sema is locked when no other request
       * can be accepted, and unlocked after receiving one reply.  */
      if (s->in_flight >= MAX_NBD_REQUESTS - 1) {
          qemu_co_mutex_lock(&s->free_sema);
          assert(s->in_flight < MAX_NBD_REQUESTS);
      }
      s->in_flight++;
  
      /* s->recv_coroutine[i] is set as soon as we get the send_lock.  */
  }
  
  static void nbd_coroutine_end(NbdClientSession *s,
      struct nbd_request *request)
  {
      int i = HANDLE_TO_INDEX(s, request->handle);
      s->recv_coroutine[i] = NULL;
      if (s->in_flight-- == MAX_NBD_REQUESTS) {
          qemu_co_mutex_unlock(&s->free_sema);
      }
  }
  
  static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
                            int nb_sectors, QEMUIOVector *qiov,
                            int offset)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
      struct nbd_request request = { .type = NBD_CMD_READ };
      struct nbd_reply reply;
      ssize_t ret;
  
      request.from = sector_num * 512;
      request.len = nb_sectors * 512;
  
      nbd_coroutine_start(client, &request);
      ret = nbd_co_send_request(bs, &request, NULL, 0);
      if (ret < 0) {
          reply.error = -ret;
      } else {
          nbd_co_receive_reply(client, &request, &reply, qiov, offset);
      }
      nbd_coroutine_end(client, &request);
      return -reply.error;
  
  }
  
  static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
                             int nb_sectors, QEMUIOVector *qiov,
                             int offset)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
      struct nbd_request request = { .type = NBD_CMD_WRITE };
      struct nbd_reply reply;
      ssize_t ret;
  
      if (!bdrv_enable_write_cache(bs) &&
          (client->nbdflags & NBD_FLAG_SEND_FUA)) {
          request.type |= NBD_CMD_FLAG_FUA;
      }
  
      request.from = sector_num * 512;
      request.len = nb_sectors * 512;
  
      nbd_coroutine_start(client, &request);
      ret = nbd_co_send_request(bs, &request, qiov, offset);
      if (ret < 0) {
          reply.error = -ret;
      } else {
          nbd_co_receive_reply(client, &request, &reply, NULL, 0);
      }
      nbd_coroutine_end(client, &request);
      return -reply.error;
  }
  
  /* qemu-nbd has a limit of slightly less than 1M per request.  Try to
   * remain aligned to 4K. */
  #define NBD_MAX_SECTORS 2040
  
  int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
                          int nb_sectors, QEMUIOVector *qiov)
  {
      int offset = 0;
      int ret;
      while (nb_sectors > NBD_MAX_SECTORS) {
          ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
          if (ret < 0) {
              return ret;
          }
          offset += NBD_MAX_SECTORS * 512;
          sector_num += NBD_MAX_SECTORS;
          nb_sectors -= NBD_MAX_SECTORS;
      }
      return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
  }
  
  int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
                           int nb_sectors, QEMUIOVector *qiov)
  {
      int offset = 0;
      int ret;
      while (nb_sectors > NBD_MAX_SECTORS) {
          ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
          if (ret < 0) {
              return ret;
          }
          offset += NBD_MAX_SECTORS * 512;
          sector_num += NBD_MAX_SECTORS;
          nb_sectors -= NBD_MAX_SECTORS;
      }
      return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);
  }
  
  int nbd_client_co_flush(BlockDriverState *bs)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
      struct nbd_request request = { .type = NBD_CMD_FLUSH };
      struct nbd_reply reply;
      ssize_t ret;
  
      if (!(client->nbdflags & NBD_FLAG_SEND_FLUSH)) {
          return 0;
      }
  
      if (client->nbdflags & NBD_FLAG_SEND_FUA) {
          request.type |= NBD_CMD_FLAG_FUA;
      }
  
      request.from = 0;
      request.len = 0;
  
      nbd_coroutine_start(client, &request);
      ret = nbd_co_send_request(bs, &request, NULL, 0);
      if (ret < 0) {
          reply.error = -ret;
      } else {
          nbd_co_receive_reply(client, &request, &reply, NULL, 0);
      }
      nbd_coroutine_end(client, &request);
      return -reply.error;
  }
  
  int nbd_client_co_discard(BlockDriverState *bs, int64_t sector_num,
                            int nb_sectors)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
      struct nbd_request request = { .type = NBD_CMD_TRIM };
      struct nbd_reply reply;
      ssize_t ret;
  
      if (!(client->nbdflags & NBD_FLAG_SEND_TRIM)) {
          return 0;
      }
      request.from = sector_num * 512;
      request.len = nb_sectors * 512;
  
      nbd_coroutine_start(client, &request);
      ret = nbd_co_send_request(bs, &request, NULL, 0);
      if (ret < 0) {
          reply.error = -ret;
      } else {
          nbd_co_receive_reply(client, &request, &reply, NULL, 0);
      }
      nbd_coroutine_end(client, &request);
      return -reply.error;
  
  }
  
  void nbd_client_detach_aio_context(BlockDriverState *bs)
  {
      aio_set_fd_handler(bdrv_get_aio_context(bs),
                         nbd_get_client_session(bs)->sock,
                         false, NULL, NULL, NULL);
  }
  
  void nbd_client_attach_aio_context(BlockDriverState *bs,
                                     AioContext *new_context)
  {
      aio_set_fd_handler(new_context, nbd_get_client_session(bs)->sock,
                         false, nbd_reply_ready, NULL, bs);
  }
  
  void nbd_client_close(BlockDriverState *bs)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
      struct nbd_request request = {
          .type = NBD_CMD_DISC,
          .from = 0,
          .len = 0
      };
  
      if (client->sock == -1) {
          return;
      }
  
      nbd_send_request(client->sock, &request);
  
      nbd_teardown_connection(bs);
  }
  
  int nbd_client_init(BlockDriverState *bs, int sock, const char *export,
                      Error **errp)
  {
      NbdClientSession *client = nbd_get_client_session(bs);
      int ret;
  
      /* NBD handshake */
      logout("session init %s\n", export);
      qemu_set_block(sock);
      ret = nbd_receive_negotiate(sock, export,
                                  &client->nbdflags, &client->size, errp);
      if (ret < 0) {
          logout("Failed to negotiate with the NBD server\n");
          closesocket(sock);
          return ret;
      }
  
      qemu_co_mutex_init(&client->send_mutex);
      qemu_co_mutex_init(&client->free_sema);
      client->sock = sock;
  
      /* Now that we're connected, set the socket to be non-blocking and
       * kick the reply mechanism.  */
      qemu_set_nonblock(sock);
      nbd_client_attach_aio_context(bs, bdrv_get_aio_context(bs));
  
      logout("Established connection with NBD server\n");
      return 0;
  }
  